Chemical mechanical polishing of tungsten using a method and composition containing quaternary phosphonium compounds

ABSTRACT

A process and composition are disclosed for polishing tungsten containing select quaternary phosphonium compounds at low concentrations to at least reduce corrosion rate of tungsten. The process and composition include providing a substrate containing tungsten; providing a stable polishing composition, containing, as initial components: water; an oxidizing agent; select quaternary phosphonium compounds at low concentrations to at least reduce corrosion rate; a dicarboxylic acid, a source of iron ions; a colloidal silica abrasive; and, optionally a pH adjusting agent; providing a chemical mechanical polishing pad, having a polishing surface; creating dynamic contact at an interface between the polishing pad and the substrate; and dispensing the polishing composition onto the polishing surface at or near the interface between the polishing pad and the substrate; wherein some of the tungsten is polished away from the substrate, and corrosion rate of tungsten is reduced.

The present application is a divisional application and claims priorityto co-pending parent patent application Ser. No. 16/270,725, filed Feb.8, 2019.

FIELD OF THE INVENTION

The present invention is directed to the field of chemical mechanicalpolishing of tungsten using a method and composition containing selectquaternary phosphonium compounds at low concentrations to at leastreduce corrosion rate. More specifically, the present invention isdirected to a method and composition of chemical mechanical polishing oftungsten using a method and composition containing select quaternaryphosphonium compounds at low concentrations to at least reduce corrosionrate of tungsten by providing a substrate containing tungsten; providinga stable polishing composition, containing, as initial components:water; an oxidizing agent; select quaternary phosphonium compounds atlow concentrations to at least reduce corrosion rate of tungsten; adicarboxylic acid, a source of iron ions; a colloidal silica abrasive;and, optionally a pH adjusting agent; providing a chemical mechanicalpolishing pad, having a polishing surface; creating dynamic contact atan interface between the polishing pad and the substrate; and dispensingthe stable polishing composition onto the polishing surface at or nearthe interface between the polishing pad and the substrate where some ofthe tungsten is polished away from the substrate.

BACKGROUND OF THE INVENTION

In the fabrication of integrated circuits and other electronic devices,multiple layers of conducting, semiconducting and dielectric materialsare deposited on or removed from a surface of a semiconductor wafer.Thin layers of conducting, semiconducting, and dielectric materials maybe deposited by a number of deposition techniques. Common depositiontechniques in modern processing include physical vapor deposition (PVD),also known as sputtering, chemical vapor deposition (CVD),plasma-enhanced chemical vapor deposition (PECVD), and electrochemicalplating (ECP).

As layers of materials are sequentially deposited and removed, theuppermost surface of the wafer becomes non-planar. Because subsequentsemiconductor processing (e.g., metallization) requires the wafer tohave a flat surface, the wafer needs to be planarized. Planarization isuseful in removing undesired surface topography and surface defects,such as rough surfaces, agglomerated materials, crystal lattice damage,scratches, and contaminated layers or materials.

Chemical mechanical planarization, or chemical mechanical polishing(CMP), is a common technique used to planarize substrates, such assemiconductor wafers. In conventional CMP, a wafer is mounted on acarrier assembly and positioned in contact with a polishing pad in a CMPapparatus. The carrier assembly provides a controllable pressure to thewafer, pressing it against the polishing pad. The pad is moved (e.g.,rotated) relative to the wafer by an external driving force.Simultaneously therewith, a polishing composition (“slurry”) or otherpolishing solution is provided between the wafer and the polishing pad.Thus, the wafer surface is polished and made planar by the chemical andmechanical action of the pad surface and slurry.

Substrates in the electronics industry possess a high degree ofintegration where semiconductor bases include multilayers ofinterconnected structures. The layers and the structures include a widevariety of materials such as single crystal silicon, polycrystallinesilicon, tetraethyl orthosilicate, silicon dioxide, silicon nitride,tungsten, titanium, titanium nitride and various other conductive,semiconductive and dielectric materials. Because these substratesrequire various processing steps, including CMP to form a finalmultilayered interconnected structure, it is often highly desirable toutilize polishing compositions and processes that are selective forspecific materials depending on the intended applications.

Chemical mechanical polishing has become a preferred method forpolishing tungsten during the formation of tungsten interconnects andcontact plugs in integrated circuit designs. Tungsten is frequently usedin integrated circuit designs for contact/via plugs. Typically, acontact or via hole is formed through a dielectric layer on a substrateto expose regions of an underlying component, for example, a first levelmetallization or interconnect.

One problem associated with polishing metals such as tungsten iscorrosion. The corrosion of tungsten is a common side-effect of CMP.During the CMP process the metal polishing slurry that remains on thesurface of the substrate continues to corrode the substrate beyond theeffects of the CMP. Sometimes corrosion is desired; however, in mostsemiconductor processes corrosion is to be reduced or inhibited.Corrosion may also contribute to surface defects such as pitting andkey-holing. These surface defects significantly affect the finalproperties of the semiconductor device and hamper its usefulness.

Another problem which may be associated with polishing tungsten isexcessive dishing of tungsten which can in-turn lead to erosion ofdielectric material. The topographical defects which can result fromsuch dishing and erosion can further lead to non-uniform removal ofadditional materials from the substrate surface, such as barrier layermaterial disposed beneath the conductive material or dielectric materialand produce a substrate surface having less than desirable quality whichcan negatively impact the performance of the integrated circuit.

Therefore, there is a need for a CMP polishing method and compositionfor tungsten where at least the corrosion rate of tungsten is reduced.

SUMMARY OF THE INVENTION

The present invention provides a method of chemical mechanical polishingtungsten, comprising: providing a substrate comprising tungsten and adielectric; providing a chemical mechanical polishing composition,comprising, as initial components: water; an oxidizing agent; acolloidal silica abrasive; a dicarboxylic acid or salt thereof; a sourceof iron (III) ions; and, optionally, a pH adjusting agent; and, aquaternary phosphonium compound in amounts of less than 1000 ppm butgreater than 0 ppm, wherein the quaternary phosphonium compound has aformula:

wherein R₁, R₂, R₃ and R₄ independently comprise hydrogen; linear orbranched alkyl; linear or branched hydroxyalkyl; linear or branchedalkoxy; linear or branched, aminoalkyl; linear or branched haloalkyl;linear or branched carboxyalkyl; acetonyl; allyl; substituted orunsubstituted aryl; substituted or unsubstituted arylalkyl; substitutedor unsubstituted arylalkoxy; alkylphosphonium moiety; or a heterocyclicalkyl moiety; with the proviso that R₁, R₂, R₃ and R₄ are not allhydrogen at the same instance and all are not butyl at the sameinstance; and X⁻ is a halide ion or hydroxide ion; providing a chemicalmechanical polishing pad, having a polishing surface; creating dynamiccontact at an interface between the chemical mechanical polishing padand the substrate; and dispensing the chemical mechanical polishingcomposition onto the polishing surface of the chemical mechanicalpolishing pad at or near the interface between the chemical mechanicalpolishing pad and the substrate; wherein some of the tungsten ispolished away from the substrate.

The present invention provides a chemical mechanical method of polishingtungsten, comprising: providing the substrate comprising tungsten and adielectric; providing a chemical mechanical polishing composition,comprising, as initial components: water; an oxidizing agent; acolloidal silica abrasive having a negative zeta potential; adicarboxylic acid or salt thereof; a source of iron (III) ions; and,optionally, a pH adjusting agent; and,

a quaternary phosphonium compound in amounts of less than 1000 ppm butgreater than 0 ppm, wherein the quaternary phosphonium compound has aformula:

wherein R₁, R₂, R₃ and R₄ independently comprise hydrogen; linear orbranched (C₁-C₂₀)alkyl; linear or branched hydroxy(C₁-C₁₀)alkyl; linearor branched (C₁-C₁₀)alkoxy; linear or branched, amino(C₁-C₈)alkyl;linear or branched halo(C₁-C₈)alkyl; linear or branchedcarboxy(C₁-C₈)alkyl; acetonyl; allyl; substituted or unsubstitutedphenyl; substituted or unsubstituted phenyl(C₁-C₈)alkyl; substituted orunsubstituted phenyl(C₁-C₈)alkoxy; (C₂-C₄)alkylphosphonium moiety; or aheterocyclic(C₁-C₅)alkyl moiety; with the proviso that R₁, R₂, R₃ and R₄are not all hydrogen at the same instance and all are not butyl at thesame instance; and X⁻ is bromide, chloride, fluoride, iodide, orhydroxide ion; providing a chemical mechanical polishing pad, having apolishing surface; creating dynamic contact at an interface between thechemical mechanical polishing pad and the substrate; and dispensing thechemical mechanical polishing composition onto the polishing surface ofthe chemical mechanical polishing pad at or near the interface betweenthe chemical mechanical polishing pad and the substrate; wherein some ofthe tungsten is polished away from the substrate; wherein the chemicalmechanical polishing composition provided has a tungsten removal rate of≥1,000 Å/min with a platen speed of 80 revolutions per minute, a carrierspeed of 81 revolutions per minute, a chemical mechanical polishingcomposition flow rate of 125 mL/min, a nominal down force of 21.4 kPa ona 200 mm polishing machine; and, wherein the chemical mechanicalpolishing pad comprises a polyurethane polishing layer containingpolymeric hollow core microparticles and a polyurethane impregnatednon-woven subpad.

The present invention provides a chemical mechanical method of polishingtungsten, comprising: providing a substrate comprising tungsten and adielectric; providing a chemical mechanical polishing composition,comprising, as initial components: water; an oxidizing agent; acolloidal silica abrasive having a negative zeta potential; malonic acidor salt thereof; a source of iron (III) ions; and, optionally, a pHadjusting agent; and,

a quaternary phosphonium compound in amounts of 5 ppm to less than 1000ppm, wherein the quaternary phosphonium compound has a formula:

wherein R₁, R₂, R₃ and R₄ independently comprise hydrogen; linear orbranched (C₁-C₁₆)alkyl; linear or branched hydroxy(C₁-C₈)alkyl; linearor branched (C₁-C₈)alkoxy; linear or branched, amino(C₁-C₈)alkyl; linearor branched halo(C₁-C₈)alkyl; linear or branched carboxy(C₁-C₈)alkyl;substituted or unsubstituted phenyl; substituted or unsubstitutedphenyl(C₁-C₈)alkyl; substituted or unsubstituted phenyl(C₁-C₈)alkoxy;(C₂-C₄)alkylphosphonium moiety; or a heterocyclic(C₁-C₅)alkyl moiety;with the proviso that R₁, R₂, R₃ and R₄ are not all hydrogen at the sameinstance and not all are butyl at the same instance; and X⁻ is bromide,chloride or fluoride; providing a chemical mechanical polishing pad,having a polishing surface; creating dynamic contact at an interfacebetween the chemical mechanical polishing pad and the substrate; anddispensing the chemical mechanical polishing composition onto thepolishing surface of the chemical mechanical polishing pad at or nearthe interface between the chemical mechanical polishing pad and thesubstrate; wherein some of the tungsten is polished away from thesubstrate; wherein the chemical mechanical polishing compositionprovided has a tungsten removal rate of ≥1,000 Å/min with a platen speedof 80 revolutions per minute, a carrier speed of 81 revolutions perminute, a chemical mechanical polishing composition flow rate of 125mL/min, a nominal down force of 21.4 kPa on a 200 mm polishing machine;wherein the chemical mechanical polishing pad comprises a polyurethanepolishing layer containing polymeric hollow core microparticles and apolyurethane impregnated non-woven subpad.

The present invention provides a method of chemical mechanical polishingtungsten, comprising: providing the substrate comprising tungsten and adielectric; providing a chemical mechanical polishing composition,comprising, as initial components: water; 0.01 to 10 wt % of anoxidizing agent, wherein the oxidizing agent is hydrogen peroxide; 0.01to 10 wt % of a colloidal silica abrasive having a negative zetapotential; 100 to 1,400 ppm malonic acid or salt thereof; 100 to 1,000ppm of a source of iron (III) ions, wherein the source of iron (III)ions is ferric nitrate nonahydrate; and, optionally, a pH adjustingagent;

a quaternary phosphonium compound in amounts of 5 ppm to 500 ppm,wherein the quaternary phosphonium compound has a formula:

wherein R₁, R₂, R₃ and R₄ independently comprise hydrogen; linear orbranched (C₁-C₁₆)alkyl; linear or branched hydroxy(C₁-C₄)alkyl; linearor branched (C₁-C₄)alkoxy; linear or branched, amino(C₁-C₄)alkyl; linearor branched halo(C₁-C₄)alkyl; linear or branched carboxy(C₁-C₄)alkyl;substituted or unsubstituted phenyl; substituted or unsubstitutedphenyl(C₁-C₄)alkyl; substituted or unsubstituted phenyl(C₁-C₄)alkoxy;(C₂-C₄)alkylphosphonium moiety; or a heterocyclic(C₁-C₃)alkyl moiety;with the proviso that R₁, R₂, R₃ and R₄ are not all hydrogen at the sameinstance and not all are butyl at the same instance; and X⁻ is bromide,chloride or fluoride; wherein the chemical mechanical polishingcomposition has a pH of 1 to 7; providing a chemical mechanicalpolishing pad, having a polishing surface; creating dynamic contact atan interface between the chemical mechanical polishing pad and thesubstrate; and dispensing the chemical mechanical polishing compositiononto the polishing surface of the chemical mechanical polishing pad ator near the interface between the chemical mechanical polishing pad andthe substrate; wherein some of the tungsten is polished away from thesubstrate.

The present invention provides a method of chemical mechanical polishingtungsten, comprising: providing a substrate comprising tungsten and adielectric; providing a chemical mechanical polishing composition,comprising, as initial components: water; 1 to 3 wt % of an oxidizingagent, wherein the oxidizing agent is hydrogen peroxide; 0.2 to 4 wt %of a colloidal silica abrasive having a negative zeta potential; 120 to1,350 ppm of malonic acid; 250 to 400 ppm of a source of iron (III)ions, wherein the source of iron (III) ions is ferric nitratenonahydrate; and, optionally, a pH adjusting agent; and,

a quaternary phosphonium compound in amounts of 5 ppm to 250 ppm,wherein the quaternary phosphonium compound has a formula:

wherein R₁, R₂, R₃ and R₄ independently comprise hydrogen; linear orbranched (C₄-C₁₆)alkyl; linear or branched hydroxy(C₁-C₄)alkyl; linearor branched, amino(C₁-C₄)alkyl; linear or branched halo(C₁-C₄)alkyl;substituted or unsubstituted phenyl; or substituted or unsubstitutedphenyl(C₁-C₄)alkyl; with the proviso that R₁, R₂, R₃ and R₄ are not allhydrogen at the same instance and are not all butyl at the sameinstance; and X⁻ is bromide or chloride; wherein the chemical mechanicalpolishing composition has a pH of 2 to 3; providing a chemicalmechanical polishing pad, having a polishing surface; creating dynamiccontact at an interface between the chemical mechanical polishing padand the substrate; and dispensing the chemical mechanical polishingcomposition onto the polishing surface of the chemical mechanicalpolishing pad at or near the interface between the chemical mechanicalpolishing pad and the substrate; wherein some of the tungsten ispolished away from the substrate.

The present invention provides a chemical mechanical polishingcomposition for tungsten comprising, as initial components: water; anoxidizing agent; a colloidal silica abrasive; a dicarboxylic acid orsalt thereof; a source of iron (III) ions; and, optionally, a pHadjusting agent; and, a quaternary phosphonium compound in amounts ofless than 1000 ppm but greater than 0 ppm, wherein the quaternaryphosphonium compound has a formula:

wherein R₁, R₂, R₃ and R₄ independently comprise hydrogen; linear orbranched alkyl; linear or branched hydroxyalkyl; linear or branchedalkoxy; linear or branched, aminoalkyl; linear or branched haloalkyl;linear or branched carboxyalkyl; substituted or unsubstituted aryl;substituted or unsubstituted arylalkyl; substituted or unsubstitutedarylalkoxy; acetonyl; allyl; alkylphosphonium moiety; or a heterocyclicalkyl moiety; with the proviso that R₁, R₂, R₃ and R₄ are not allhydrogen at the same instance and all are not butyl at the sameinstance; and X⁻ is a halide ion or hydroxide ion.

The present invention provides a chemical mechanical polishingcomposition for tungsten comprising, as initial components: water; anoxidizing agent; a colloidal silica abrasive having a negative zetapotential; a dicarboxylic acid or salt thereof; a source of iron (III)ions; and, optionally, a pH adjusting agent; and, a quaternaryphosphonium compound in amounts of 5 ppm to less than 1000 ppm, whereinthe quaternary phosphonium compound has a formula:

wherein R₁, R₂, R₃ and R₄ independently comprise hydrogen; linear orbranched (C₁-C₂₀)alkyl; linear or branched hydroxy(C₁-C₁₀)alkyl; linearor branched (C₁-C₁₀)alkoxy; linear or branched, amino(C₁-C₈)alkyl;linear or branched halo(C₁-C₈)alkyl; linear or branchedcarboxy(C₁-C₈)alkyl; acetonyl; allyl; substituted or unsubstitutedphenyl; substituted or unsubstituted phenyl(C₁-C₈)alkyl; substituted orunsubstituted phenyl(C₁-C₈)alkoxy; (C₂-C₄)alkylphosphonium moiety; or aheterocyclic(C₁-C₅)alkyl moiety; with the proviso that R₁, R₂, R₃ and R₄are not all hydrogen at the same instance and all are not butyl at thesame instance; and X⁻ is bromide, chloride, fluoride, iodide orhydroxide ion.

The present invention provides a chemical mechanical polishingcomposition for tungsten comprising: water; 0.01 to 10 wt % of anoxidizing agent, wherein the oxidizing agent is hydrogen peroxide; 0.01to 10 wt % of a colloidal silica abrasive having a negative zetapotential; 100 to 1,400 ppm malonic acid or salt thereof; 100 to 1,000ppm of a source of iron (III) ions, wherein the source of iron (III)ions is ferric nitrate; and, optionally, a pH adjusting agent, whereinthe pH of the chemical mechanical polishing composition is from 1 to 7;and, a quaternary phosphonium compound in amounts of 5 ppm to 500 ppm,wherein the quaternary phosphonium compound has a formula:

wherein R₁, R₂, R₃ and R₄ independently comprise hydrogen; linear orbranched (C₁-C₁₆)alkyl; linear or branched hydroxy(C₁-C₄)alkyl; linearor branched (C₁-C₄)alkoxy; linear or branched, amino(C₁-C₄)alkyl; linearor branched halo(C₁-C₄)alkyl; linear or branched carboxy(C₁-C₄)alkyl;acetonyl; substituted or unsubstituted phenyl; substituted orunsubstituted phenyl(C₁-C₄)alkyl; substituted or unsubstitutedphenyl(C₁-C₄)alkoxy; (C₂-C₄)alkylphosphonium moiety; or aheterocyclic(C₁-C₃)alkyl moiety; with the proviso that R₁, R₂, R₃ and R₄are not all hydrogen at the same instance and are not all butyl at thesame instance; and X⁻ is bromide, chloride, fluoride, iodide orhydroxide ion.

The present invention provides a chemical mechanical polishingcomposition, comprising, as initial components: water; 0.01 to 10 wt %of an oxidizing agent, wherein the oxidizing agent is hydrogen peroxide;0.01 to 10 wt % of a colloidal silica abrasive having a negative zetapotential; 100 to 1,400 ppm malonic acid or salt thereof; 100 to 1,000ppm of a source of iron (III) ions, wherein the source of iron (III)ions is ferric nitrate nonahydrate; and, optionally, a pH adjustingagent; a quaternary phosphonium compound in amounts of 5 ppm to 250 ppm,wherein the quaternary phosphonium compound has a formula:

wherein R₁, R₂, R₃ and R₄ independently comprise hydrogen; linear orbranched (C₁-C₁₆)alkyl; linear or branched hydroxy(C₁-C₄)alkyl; linearor branched (C₁-C₄)alkoxy; linear or branched, amino(C₁-C₄)alkyl; linearor branched halo(C₁-C₄)alkyl; linear or branched carboxy(C₁-C₄)alkyl;substituted or unsubstituted phenyl; substituted or unsubstitutedphenyl(C₁-C₄)alkyl; substituted or unsubstituted phenyl(C₁-C₄)alkoxy;(C₂-C₄)alkylphosphonium moiety; or a heterocyclic(C₁-C₃)alkyl moiety;with the proviso that R₁, R₂, R₃ and R₄ are not all hydrogen at the sameinstance and are not all butyl at the same instance; and X⁻ is bromide,chloride or fluoride.

The present invention provides a chemical mechanical polishingcomposition for tungsten, comprising, as initial components: water; 1 to3 wt % of an oxidizing agent, wherein the oxidizing agent is hydrogenperoxide; 0.2 to 4 wt % of a colloidal silica abrasive having a negativezeta potential; 120 to 1,350 ppm of malonic acid; 250 to 400 ppm of asource of iron (III) ions, wherein the source of iron (III) ions isferric nitrate nonahydrate; and, optionally, a pH adjusting agent,wherein the pH of the chemical mechanical polishing composition is from2 to 3; and, a quaternary phosphonium compound in amounts of 10 ppm 100ppm, wherein the quaternary phosphonium compound has a formula:

wherein R₁, R₂, R₃ and R₄ independently comprise hydrogen; linear orbranched (C₄-C₁₆)alkyl; linear or branched hydroxy(C₁-C₄)alkyl; linearor branched, amino(C₁-C₄)alkyl; linear or branched halo(C₁-C₄)alkyl;substituted or unsubstituted phenyl; substituted or unsubstitutedphenyl(C₁-C₄)alkyl; with the proviso that R₁, R₂, R₃ and R₄ are not allhydrogen at the same instance and are not all liear butyl at the sameinstance; and X⁻ is bromide or chloride.

The foregoing methods of the present invention use a stable chemicalmechanical polishing composition comprising select quaternaryphosphonium compounds at concentrations of less than 1000 ppm butgreater than 0 ppm to at least reduce corrosion rate of tungsten (W) andpolish the tungsten (W).

DETAILED DESCRIPTION OF THE INVENTION

As used throughout this specification the following abbreviations havethe following meanings, unless the context indicates otherwise: °C.=degrees Centigrade; g=grams; L=liters; mL=milliliters; μ=μm=microns;kPa=kilopascal; Å=angstroms; mV=millivolts; DI=deionized; ppm=parts permillion=mg/L; mm=millimeters; cm=centimeter; nm=nanometers; min=minute;rpm=revolutions per minute; lbs=pounds; kg=kilograms; W=tungsten;P=phosphorous; halide ions=bromide, chloride, fluoride and iodide;bromide=Br⁻; chloride=Cl⁻; fluoride=F⁻; iodide=I⁻; X⁻=counter anion;PPh₄=tetraphenyl phosphonium bromide; P[6,6,6,14]=trihexyltetradecylphosphonium chloride; DiP⁺=1,3-propanediyl-bis(tripropylphosphonium)difluoride; TriP⁺=1,3,5-tris[(tripropylphosphonium) methyl] benzenetrifluoride; P[1,1,1,1]=tetrakis(hydroxymethyl) phosphonium chloride;P[4,4,4,16]=hexadecyltributyl phosphonium bromide;P[4,4,4,8]=tributyl-n-octylphosphonium bromide; P[4,4,4,12]=tributyldodecylphosphonium bromide; P[4,4,4,4]=tetrabutylphosphonium hydroxide(hydroxide ion salt); ICP-OES=inductively coupled plasma opticalemission spectroscopy; wt %=percent by weight; RR=removal rate;CS=Control Slurry; SC=comparative slurry.

The term “chemical mechanical polishing” or “CMP” refers to a processwhere a substrate is polished by means of chemical and mechanical forcesalone and is distinguished from electrochemical-mechanical polishing(ECMP) where an electric bias is applied to the substrate. The term“TEOS” means the silicon dioxide formed from the decomposition oftetraethyl orthosilicate (Si(OC₂H₅)₄). The term “moiety” means a part orfunctional group of a molecule. The terms “a” and “an” refer to both thesingular and the plural. All percentages are by weight, unless otherwisenoted. All numerical ranges are inclusive and combinable in any order,except where it is logical that such numerical ranges are constrained toadd up to 100%.

The method of polishing a substrate of the present invention uses achemical mechanical polishing composition containing an oxidizing agent;a colloidal silica abrasive; a dicarboxylic acid or salt thereof; asource of iron (III) ions; and, optionally, a pH adjusting agent and aquaternary phosphonium compound in amounts of less than 1000 ppm butgreater than 0 ppm, where the quaternary phosphonium compound has aformula:

where R₁, R₂, R₃ and R₄ independently comprise hydrogen; linear orbranched alkyl; linear or branched hydroxyalkyl; linear or branchedalkoxy; linear or branched, aminoalkyl; linear or branched haloalkyl;linear or branched carboxyalkyl; substituted or unsubstituted aryl;substituted or unsubstituted arylalkyl; substituted or unsubstitutedarylalkoxy; acetonyl; allyl; phosphoniumalkyl moiety; or a heterocyclicalkyl moiety; with the proviso that R₁, R₂, R₃ and R₄ are not allhydrogen at the same instance and not all are butyl at the sameinstance; and X⁻ is a halide ion or hydroxide ion, to provide for theremoval of tungsten from the substrate surface while reducing at leastcorrosion rate of the tungsten.

Preferably, the method of polishing a substrate of the presentinvention, comprises: providing the substrate, wherein the substratecomprises tungsten and a dielectric; providing a chemical mechanicalpolishing composition, comprising, preferably, consisting of, as initialcomponents: water; an oxidizing agent, preferably in amounts of at least0.01 wt % to 10 wt %, more preferably in amounts of 0.1 wt % to 5 wt %,still more preferably from 1 wt % to 3 wt %; a colloidal silicaabrasive, preferably in amounts of 0.01 wt % to 10 wt %, more preferablyfrom 0.05 wt % to 7.5 wt %, even more preferably from 0.1 wt % to 5 wt%, still more preferably from 0.2 wt % to 4 wt %; a dicarboxylic acid,salt thereof or mixtures thereof, preferably in amounts of 100 ppm to1400 ppm, more preferably from 120 ppm to 1350 ppm; a source of iron(III) ions, preferably, wherein the source of iron (III) ions is ferricnitrate nonahydrate; and, optionally, a pH adjusting agent; preferably,wherein the chemical mechanical polishing composition has a pH of 1 to7; more preferably, of 1.5 to 4.5; still more preferably, 1.5 to 3.5;most preferably, of 2 to 3; and a quaternary phosphonium compound inamounts of less than 1000 ppm but greater than 0 ppm, where thequaternary phosphonium compound has a formula:

where R₁, R₂, R₃ and R₄ independently comprise hydrogen; linear orbranched (C₁-C₂₀)alkyl; linear or branched hydroxy(C₁-C₁₀)alkyl; linearor branched (C₁-C₁₀)alkoxy; linear or branched, amino(C₁-C₈)alkyl;linear or branched halo(C₁-C₈)alkyl; linear or branchedcarboxy(C₁-C₈)alkyl; substituted or unsubstituted phenyl; substituted orunsubstituted phenyl(C₁-C₈)alkyl; substituted or unsubstitutedphenyl(C₁-C₈)alkoxy; acetonyl; allyl; (C₂-C₄)alkylphosphonium moiety; ora heterocyclic(C₁-C₅)alkyl moiety; with the proviso that R₁, R₂, R₃ andR₄ are not all hydrogen at the same instance and all are not butyl atthe same instance; and X⁻ is a halogen ion or hydroxide ion; providing achemical mechanical polishing pad, having a polishing surface; creatingdynamic contact at an interface between the chemical mechanicalpolishing pad and the substrate; and dispensing the chemical mechanicalpolishing composition onto the polishing surface of the chemicalmechanical polishing pad at or near the interface between the chemicalmechanical polishing pad and the substrate; wherein at least some of thetungsten is polished away from the substrate.

Preferably, in the method of polishing a substrate of the presentinvention, the substrate comprises tungsten and a dielectric. Morepreferably, the substrate provided is a semiconductor substratecomprising tungsten and a dielectric. Most preferably, the substrateprovided is a semiconductor substrate comprising tungsten depositedwithin at least one of holes and trenches formed in a dielectric such asTEOS.

Preferably, in the method of polishing a substrate of the presentinvention, the water contained, as an initial component, in the chemicalmechanical polishing composition provided is at least one of deionizedand distilled to limit incidental impurities.

Preferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing composition providedcontains, as an initial component, an oxidizing agent, wherein theoxidizing agent is selected from the group consisting of hydrogenperoxide (H₂O₂), monopersulfates, iodates, magnesium perphthalate,peracetic acid and other per-acids, persulfate, bromates, perbromate,persulfate, peracetic acid, periodate, nitrates, iron salts, ceriumsalts, Mn (III), Mn (IV) and Mn (VI) salts, silver salts, copper salts,chromium salts, cobalt salts, halogens, hypochlorites and a mixturethereof. More preferably, the oxidizing agent is selected from hydrogenperoxide, perchlorate, perbromate; periodate, persulfate and peraceticacid. Most preferably, the oxidizing agent is hydrogen peroxide.

Preferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing composition providedcontains, as an initial component, 0.01 to 10 wt %, more preferably, 0.1to 5 wt %; most preferably, 1 to 3 wt % of an oxidizing agent.

Preferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing composition providedcontains, as an initial component, a source of iron (III) ions. Morepreferably, in the method of the present invention, the chemicalmechanical polishing composition provided contains, as an initialcomponent, a source of iron (III) ions, wherein the source of iron (III)ions is selected from the group consisting of iron (III) salts. Mostpreferably, in the method of the present invention, the chemicalmechanical polishing composition provided contains, as an initialcomponent, a source of iron (III) ions, wherein the source of iron (III)ions is ferric nitrate nonahydrate, (Fe(NO₃)₃·9H₂O).

Preferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing composition providedcontains, as an initial component, a source of iron (III) ionssufficient to introduce 1 to 200 ppm, preferably, 5 to 150 ppm, morepreferably, 7.5 to 125 ppm, most preferably, 10 to 100 ppm of iron (III)ions to the chemical mechanical polishing composition.

Preferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing composition providedcontains, as an initial component, a source of iron (III) ions. Morepreferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing composition providedcontains, as an initial component, 100 to 1,000 ppm, preferably, 150 to750 ppm, more preferably, 200 to 500 ppm and most preferably, 250 to 400ppm of a source of iron (III) ions. Most preferably, in the method ofpolishing a substrate of the present invention, the chemical mechanicalpolishing composition provided contains, as an initial component, 100 to1,000 ppm, preferably, 150 to 750 ppm, more preferably, 200 to 500 ppm,most preferably, 250 to 400 ppm of a source of iron (III) ions, whereinthe source of iron (III) ions is ferric nitrate nonahydrate,(Fe(NO₃)₃·9H₂O).

Preferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing composition providedcontains, as an initial component, a quaternary phosphonium compound inamounts of less than 1000 ppm but greater than 0 ppm having a formula:

where R₁, R₂, R₃ and R₄ independently comprise hydrogen; linear orbranched (C₁-C₂₀)alkyl, preferably linear or branched (C₁-C₁₆)alkyl,more preferably linear or branched (C₄-C₁₆) alkyl; linear or branchedhydroxy(C₁-C₁₀)alky, more preferably linear or branchedhydroxy(C₁-C₈)alky, even more preferably linear or branchedhydroxy(C₁-C₄)alkyl; linear or branched (C₁-C₁₀)alkoxy, preferablylinear or branched (C₁-C₈)alkoxy, more preferably linear or branched(C₁-C₄)alkoxy; linear or branched, amino(C₁-C₈)alkyl, more preferablylinear or branched amino(C₁-C₄)alkyl; linear or branchedhalo(C₁-C₈)alkyl, more preferably linear or branched halo(C₁-C₄)alkyl;linear or branched carboxy(C₁-C₈)alkyl, more preferably linear orbranched carboxy(C₁-C₄)alkyl; acetonyl; allyl; substituted orunsubstituted aryl, preferably substituted or unsubstituted phenyl;substituted or unsubstituted phenyl(C₁-C₈)alkyl, preferably substitutedor unsubstituted phenyl(C₁-C₄)alkyl; substituted or unsubstitutedphenyl(C₁-C₈)alkoxy, preferably substituted or unsubstitutedphenyl(C₁-C₄)alkoxy; (C₂-C₄)alkylphosphonium moiety, preferably a(C₄)alkylphosphonium moiety; or a heterocyclic(C₁-C₅)alkyl moiety suchas a dioxolan(C₁-C₂)alkyl moiety or pyridyl(C₁-C₂)alkyl moiety,preferably a heterocyclic(C₁-C₂)alkyl moiety where the heterocyclicmoiety is a dioxolan moiety; and with the proviso that R₁, R₂, R₃ and R₄are not all hydrogen at the same instance and, preferably, are not allbutyl (C₄)alkyl at the same instance; and X⁻ is a bromide, chloride,fluoride, iodide or hydroxide ion with the proviso that when X⁻ ishydroxide ion R₁, R₂, R₃ and R₄ cannot be butyl in the same instance,preferably X⁻ is bromide, chloride or fluoride, more preferably bromideor chloride. It is even more preferred that R₁, R₂ and R₃ are linear orbranched (C₄-C₈)alkyl and R₄ is linear or branched (C₈-C₁₆)alkyl, and itis most preferred that R₁, R₂ and R₃ are linear (C₄)alkyl, and R₄ islinear (C₈)alkyl, (C₁₂)alkyl or (C₁₆)alkyl. It is also preferred thatwhen R₁, R₂, R₃ and R₄ are hydroxyalkyl, R₁, R₂, R₃ and R₄ areindependently chosen from hydroxy(C₁-C₂)alkyl, most preferably R₁, R₂,R₃, and R₄ are hydroxy(C₁)alkyl or hydroxymethyl moiety. Substituentgroups on the aryl moiety, preferably the phenyl moiety, includesulfonyl; nitro; cyano; hydroxyl; hydroxyalkyl, alkoxy; alkoxyalkyl;halo group, where the halo group is preferably bromine or chlorine;haloalkyl; and (C₁-C₄)alkylphosphonium, more preferably(C₃)alkylphosphonium.

Examples of compounds of the present invention are hexadecyltributylphophonium bromide, tributyldodecylphosphonium bromide,tributyl-n-octylphosphonium bromide, tetra-n-octylphosphonium bromide,trihexyltetradecyl phosphonium chloride, tetrakis(hydroxymethyl)phosphonium chloride, tetraphenyl phosphonium bromide, methyl triphenylphosphonium bromide, triphenyl phosphonium ylide, benzyl triphenylphosphonium bromide, triphenyl(bromomethyl) phosphonium bromide,[(benzyloxy)methyl](triphenyl) phosphonium chloride, isopropyl triphenylphosphonium bromide, allyltriphenyl phosphonium chloride,acetonyltriphenyl phosphonium chloride, (3-aminopropyl)(triphenyl)phosphonium bromide, tetrakis(diethylamino)phosphonium bromide,tributyl-2-4-dichlorobenzyl-phosphonium chloride, ethyltriphenylphosphonium bromide, triphenyl (2-pyridylmethyl) phosphonium chloride,tributyl (1,3-dioxolan-2-ylmethyl) phosphonium bromide,1,3-propanediyl-bis(tripropylphosphonium) difluoride and1,3,5-tris[(tripropylphosphonium)methyl]benzene trifluoride. Examples ofpreferred compounds of the present invention are hexadecyltributylphophonium bromide, tributyldodecylphosphonium bromide,tributyl-n-octylphosphonium bromide, tetra-n-octylphosphonium bromideand tetrakis(hydroxymethyl) phosphonium chloride. The most preferredcompounds of the present invention are hexadecyltributyl phosphoniumbromide, tributyldodecylphosphonium bromide, tributyl-n-octylphosphoniumbromide and tetrakis(hydroxymethyl) phosphonium chloride.

Preferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing composition providedcontains, as an initial component less than 1000 ppm but greater than 0ppm, more preferably 5 ppm to less than 1000 ppm, even more preferablyfrom 5 ppm to 500 ppm, still more preferably from 5 ppm to 250 ppm, andmost preferably from 10 ppm to 100 ppm of the quaternary phosphoniumcompounds of the present invention.

Preferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing composition providedcontains a colloidal silica abrasive having a negative zeta potential. Anegative zeta potential is preferred because a colloidal silica abrasivehaving a positive zeta potential can aggravate tungsten dishing anderosion. More preferably, in the method of polishing a substrate of thepresent invention, the chemical mechanical polishing compositionprovided contains a colloidal silica abrasive having a permanentnegative zeta potential, wherein the chemical mechanical polishingcomposition has a pH of 1 to 7, preferably, of 1.5 to 4.5; morepreferably, of 1.5 to 3.5; still more preferably, of 2 to 3. Still morepreferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing composition providedcontains a colloidal silica abrasive having a permanent negative zetapotential, wherein the chemical mechanical polishing composition has apH of 1 to 7, preferably, of 1.5 to 4.5; more preferably, of 1.5 to 3.5;still more preferably, of 2 to 3 as indicated by a zeta potential from−0.1 mV to −20 mV.

Preferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing composition providedcontains, as an initial component, a colloidal silica abrasive, whereinthe colloidal silica abrasive has an average particle size ≤200 nm,preferably, 5 to 150 nm; more preferably, 10 to 100 nm; most preferably,20 to 60 nm as measured by dynamic light scattering techniques.

Preferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing composition providedcontains 0.01 to 10 wt %, preferably 0.05 to 7.5 wt %, more preferably,0.1 to 5 wt %, most preferably, 0.2 to 4 wt % of a colloidal silicaabrasive. Preferably the colloidal silica abrasive has a negative zetapotential.

Preferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing composition providedcontains, as an initial component, a dicarboxylic acid, salts thereof,or mixtures thereof, wherein the dicarboxylic acid includes, but is notlimited to malonic acid, oxalic acid, succinic acid, adipic acid, maleicacid, malic acid, glutaric acid, tartaric acid, salts thereof ormixtures thereof. More preferably, in the method of polishing asubstrate of the present invention, the chemical mechanical polishingcomposition provided contains, as an initial component, a dicarboxylicacid, wherein the dicarboxylic acid is selected from the groupconsisting of malonic acid, oxalic acid, succinic acid, tartaric acid,salts thereof and mixtures thereof. Still more preferably the chemicalmechanical polishing composition provided contains, as an initialcomponent, a dicarboxylic acid, wherein the dicarboxylic acid isselected from the group consisting of malonic acid, oxalic acid,succinic acid, salts thereof and mixtures thereof. Most preferably inthe method of polishing a substrate of the present invention, thechemical mechanical polishing composition provided contains, as aninitial component, the dicarboxylic acid malonic acid, salts thereof, ormixtures thereof.

Preferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing composition providedcontains, as an initial component, 1 to 2,600 ppm, preferably, 100 to1,400 ppm, more preferably, 120 to 1,350 ppm, still more preferably, 130to 1,100 ppm, of a dicarboxylic acid, salt thereof, or mixtures thereof,wherein the dicarboxylic acid includes, but is not limited to malonicacid, oxalic acid, succinic acid, adipic acid, maleic acid, malic acid,glutaric acid, tartaric acid, salts thereof or mixtures thereof. Morepreferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing composition providedcontains, as an initial component, 1 to 2,600 ppm of a dicarboxylicacid, salt thereof, or mixtures thereof. Most preferably, in the methodof polishing a substrate of the present invention, the chemicalmechanical polishing composition provided contains, as an initialcomponent 100 to 1,400 ppm, more preferably, 120 to 1,350 ppm, stillmore preferably, 130 to 1,350 ppm, the dicarboxylic acid malonic acid,salts thereof, or mixtures thereof.

Preferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing composition provided has apH of 1 to 7. More preferably, in the method of polishing a substrate ofthe present invention, the chemical mechanical polishing compositionprovided has a pH of 1.5 to 4.5. Still more preferably, in the method ofpolishing a substrate of the present invention, the chemical mechanicalpolishing composition provided has a pH of 1.5 to 3.5. Most preferably,in the method of polishing a substrate of the present invention, thechemical mechanical polishing composition provided has a pH of 2 to 3.

Preferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing composition providedoptionally contains a pH adjusting agent. Preferably, the pH adjustingagent is selected from the group consisting of inorganic and organic pHadjusting agents. Preferably, the pH adjusting agent is selected fromthe group consisting of inorganic acids and inorganic bases. Morepreferably, the pH adjusting agent is selected from the group consistingof phosphoric acid and potassium hydroxide. Most preferably, the pHadjusting agent is potassium hydroxide.

Preferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing pad provided can by anysuitable polishing pad known in the art. One of ordinary skill in theart knows to select an appropriate chemical mechanical polishing pad foruse in the method of the present invention. More preferably, in themethod of polishing a substrate of the present invention, the chemicalmechanical polishing pad provided is selected from woven and non-wovenpolishing pads. Still more preferably, in the method of polishing asubstrate of the present invention, the chemical mechanical polishingpad provided comprises a polyurethane polishing layer. Most preferably,in the method of polishing a substrate of the present invention, thechemical mechanical polishing pad provided comprises a polyurethanepolishing layer containing polymeric hollow core microparticles and apolyurethane impregnated non-woven subpad. Preferably, the chemicalmechanical polishing pad provided has at least one groove on thepolishing surface.

Preferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing composition provided isdispensed onto a polishing surface of the chemical mechanical polishingpad provided at or near an interface between the chemical mechanicalpolishing pad and the substrate.

Preferably, in the method of polishing a substrate of the presentinvention, dynamic contact is created at the interface between thechemical mechanical polishing pad provided and the substrate with a downforce of 0.69 to 34.5 kPa normal to a surface of the substrate beingpolished.

Preferably, in the method of polishing a substrate of the presentinvention, wherein the chemical mechanical polishing compositionprovided has a tungsten removal rate ≥1,000 Å/min; preferably, ≥1,500Å/min; more, ≥2,000 Å/min. More preferably, in the method of polishing asubstrate of the present invention, wherein the chemical mechanicalpolishing composition provided has a tungsten removal rate of ≥1,000Å/min; preferably, ≥1,500 Å/min; more preferably, ≥2,000 Å/min; and aW/TEOS selectivity of ≥5. Still more preferably, in the method ofpolishing a substrate of the present invention, wherein the tungsten isremoved from the substrate at a removal rate of ≥1,000 Å/min;preferably, ≥1,500 Å/min; more preferably, ≥2,000 Å/min; and a W/TEOSselectivity of 5 to 20. Most preferably, in the method of polishing thesubstrate of the present invention, wherein the tungsten is removed fromthe substrate at a removal rate of ≥1,000 Å/min; preferably, ≥1,500Å/min; more preferably, ≥2,000 Å/min; and a W/TEOS selectivity and witha platen speed of 80 revolutions per minute, a carrier speed of 81revolutions per minute, a chemical mechanical polishing composition flowrate of 125 mL/min, a nominal down force of 21.4 kPa on a 200 mmpolishing machine; and, wherein the chemical mechanical polishing padcomprises a polyurethane polishing layer containing polymeric hollowcore microparticles and a polyurethane impregnated non-woven subpad.

As is illustrated in the following Examples, the tungsten CMP methodsand compositions of the present invention containing select quaternaryphosphonium compounds at concentrations of less than 1000 ppm butgreater than 0 can at least reduce corrosion rate of tungsten.

Example 1 Quaternary Phosphonium Slurry Formulations

The chemical mechanical polishing compositions of this Example wereprepared by combining the components in the amounts listed in Table 1with the balance being DI water and adjusting the pH of the compositionsto the final pH listed in Table 1 with 45 wt % potassium hydroxide.

TABLE 1 Quaternary Abra- Phosphonium Malonic Slurry sive¹ CompoundFe(NO₃)₃ Acid H₂O₂ # (wt %) (ppm) (ppm) (ppm) (wt %) pH CS1 2 — 362 13202 2.3 S1 2 P[1, 1, 1, 1] 100 362 1320 2 2.3 S2 2 P[1, 1, 1, 1] 250 3621320 2 2.3 S3 2 P[1, 1, 1, 1] 500 362 1320 2 2.3 S4 2 PPh₄ 50 362 1320 22.3 S5 2 PPh₄ 250 362 1320 2 2.3 S6 2 P[6, 6, 6, 14] 50 362 1320 2 2.3S7 2 P[6, 6, 6, 14] 250 362 1320 2 2.3 S8 2 DiP⁺ 150 362 1320 2 2.3 S9 2DiP⁺ 750 362 1320 2 2.3 S10 2 TriP⁺ 150 362 1320 2 2.3 S11 2 TriP⁺ 750362 1320 2 2.3 S12 2 P[4, 4, 4, 16] 30 362 1320 2 2.3 S13 2 P[4, 4, 4,16] 250 362 1320 2 2.3 ¹KLEBOSOL ™ 1598-B25 (−) zeta potential abrasiveslurry manufactured by AZ Electronics Materials, available from The DowChemical Company.

Example 2 Corrosion Rate Inhibition Performance of QuaternaryPhosphonium CMP Slurries

The corrosion tests were carried out by immersing W blanket wafers (1cm×4 cm) in 15 g slurry samples. The W wafers were removed from testedslurries after 10 min. The solutions were subsequently centrifuged for20 min at 9,000 rpm to remove slurry particles. The supernatant wasanalyzed by ICP-OES to determine the amount of tungsten by weight. Thecorrosion rate (Å/min) was converted from the W mass assuming an etchingwafer surface area of 4 cm². The results of the corrosion tests are inTable 2.

TABLE 2 Slurry # W Corrosion Rate (Å/min) CS1 28 S1 22 S2 19 S3 18 S4 27S5 29 S6 21 S7 14 S8 22 S9 5.3  S10 12  S11 4.1  S12 22  S13 0.4

Overall, the results of the corrosion rate tests showed that thechemical mechanical polishing slurries containing quaternary phosphoniumcompounds effectively reduced the corrosion on W containing wafers incontrast to the control (CS1) which excluded the quaternary phosphoniumcompounds.

Example 3 Quaternary Phosphonium Slurry Formulations

The chemical mechanical polishing compositions of this Example wereprepared by combining the components in the amounts listed in Table 3with the balance being DI water and adjusting the pH of the compositionsto the final pH listed in Table 3 with 45 wt % potassium hydroxide.

TABLE 3 Quaternary Abra- Phosphonium Malonic Slurry sive¹ CompoundFe(NO₃)₃ Acid H₂O₂ # (wt %) (ppm) (ppm) (ppm) (wt %) pH CS2 2 — 362 13202 2.3 S14 2 P[4, 4, 4, 8] 362 1320 2 2.3 80 S15 2 P[4, 4, 4, 12] 3621320 2 2.3 20 S16 2 P[4, 4, 4, 12] 362 1320 2 2.3 50 S17 2 P[4, 4, 4,12] 362 1320 2 2.3 80 S18 2 P[4, 4, 4, 16] 362 1320 2 2.3 20 ¹KLEBOSOL ™1598-B25 (−) zeta potential abrasive slurry manufactured by AZElectronics Materials, available from The Dow Chemical Company.

Example 4 Chemical Mechanical Polishing—Dishing and Erosion Performanceof Quaternary Phosphonium CMP Slurries

The polishing experiments were performed on 200 mm blanket wafersinstalled on an Applied Materials 200 mm MIRRA® polishing machine. Thepolishing removal rate experiments were performed on 200 mm blanket 15kÅ-thick TEOS sheet wafers from Novellus and W, blanket wafers availablefrom WaferNet Inc., Silicon Valley Microelectronics. All polishingexperiments were performed using an IC1010™ polyurethane polishing padpaired with an SP2310 subpad (commercially available from Rohm and HaasElectronic Materials CMP Inc.) with a typical down pressure of 21.4 kPa(3.1 psi), a chemical mechanical polishing composition flow rate of 125mL/min, a table rotation speed of 80 rpm and a carrier rotation speed of81 rpm unless specified otherwise. A Kinik PDA33A-3 diamond padconditioner (commercially available from Kinik Company) was used todress the polishing pad. The polishing pad was broken in with theconditioner using a down force of 9.0 lbs (4.1 kg) for 15 minutes and7.0 lbs (3.2 kg) for 15 minutes at 80 rpm (platen)/36 rpm (conditioner).The polishing pad was further conditioned ex-situ prior to polishingusing a down force of 7 lbs (3.2 kg) for 24 seconds. The TEOS erosiondepths were determined by measuring the film thickness before and afterpolishing using a KLA-Tencor FX200 metrology tool. The W removal anddishing rates were determined using a KLA-Tencor RS100C metrology tool.The wafers had varying standard line width features as shown in Tables4A and 4B. In the tables of this example the numerator refers to W andthe denominator refers to TEOS.

4A Slur- 50/50 μm 50/50 μm 10/10 μm 10/10 μm 7/3 μm 7/3 μm ry dishingerosion dishing erosion dishing erosion # (Å) (Å) (Å) (Å) (Å) (Å) CS21357 44 728 234 472 628 S14 1200 21 687 177 437 529 S15 1307 24 694 247444 580 S16 1161 23 587 214 378 601 S17 1091 24 560 253 339 573 S18 118333 628 231 395 531

TABLE 4B 9/1 μm 9/1 μm 0.25/0.25 μm 0.25/0.25 μm dishing erosion dishingerosion Slurry # (Å) (Å) (Å) (Å) CS2 364 1230 184 434 S14 333 987 157371 S15 346 1049 163 258 S16 232 1157 142 391 S17 245 944 133 483 S18289 968 132 291

Overall the quaternary phosphonium compounds showed decreased tungstendishing and TEOS erosion in view of the control polishing composition atthe feature sizes disclosed in the tables.

Example 5 Quaternary Phosphonium Slurry Formulations

The chemical mechanical polishing compositions of this Example wereprepared by combining the components in the amounts listed in Table 5with the balance being DI water and adjusting the pH of the compositionsto the final pH listed in Table 5 with 45 wt % potassium hydroxide.

TABLE 5 Quaternary Slur- Abra- Phosphonium Malonic ry sive¹ CompoundFe(NO₃)₃ Acid H₂O₂ # (wt %) (ppm) (ppm) (ppm) (wt %) pH CS3 2 — 362 13202 2.3 S19 2 P[6, 6, 6, 14] 362 1320 2 2.3 100 S20 2 P[6, 6, 6, 14] 3621320 2 2.3 500 ¹KLEBOSOL ™ 1598-B25 (−) zeta potential abrasive slurrymanufactured by AZ Electronics Materials, available from The DowChemical Company.

Example 6 Chemical Mechanical Polishing—Dishing and Erosion Performanceof Quaternary Phosphonium CMP Slurries

The chemical mechanical polishing steps, parameters and W and TEOS wafersubstrates for testing the dishing and erosion of W and TEOS,respectively, for the slurry formulations: CS3 (control), S19 and S20were substantially the same as those described in Example 4 above. Theresults are disclosed in Tables 6A and 6B. In the tables of this examplethe numerator refers to W and the denominator refers to TEOS.

6A Slur- 100/100 μm 100/100 μm 50/50 μm 50/50 μm 10/10 μm 10/10 μm rydishing erosion dishing erosion dishing erosion # (Å) (Å) (Å) (Å) (Å)(Å) CS3 1623 62 1473 144 815 565 S19 1043 11 1028 23 614 215 S20 952 3893 15 542 186

6B Slur- 7/3 μm 7/3 μm 9/1 μm 9/1 μm 0.25/0.25 μm 0.25/0.25 μm rydishing erosion dishing erosion dishing erosion # (Å) (Å) (Å) (Å) (Å)(Å) CS3 342 1191 196 1527 151 907 S19 379 581 292 955 160 333 S20 338256 256 798 147 323

Overall the tungsten dishing and the TEOS erosion were reduced when thequaternary phosphonium compounds P[6,6,6,14] were included in thepolishing composition. Best results were achieved at the larger featuresizes of 100/100 μm, 50/50 μm and 10/10 μm.

Example 7 W, TEOS Removal Rate and W, TEOS Maximum Polishing Temperature

The polishing experiments for W and TEOS removal rates were performedsubstantially as described in Example 4 using the same apparatus andparameters. The wafers were from WaferNet Inc., or Silicon ValleyMicroelectronics. The results are in Table 7.

TABLE 7 W RR TEOS RR W/TEOS W Temp. TEOS Temp. Slurry # (Å/min) (Å/min)Selectivity (° C.) (° C.) CS2 1967 173 11.4 39 35 S14 2379 188 12.6 3732 S15 2445 162 15.1 39 33 S16 2419 186 13 38 33.5 S17 2049 189 10.9 3432.5The quaternary phosphonium chemical mechanical polishing compositions ofthe present invention showed overall good W RR of greater than 2000Å/min and good W/TEOS selectivity.

Example 8 Quaternary Phosphonium Slurry Formulations and Stability Test

The chemical mechanical polishing compositions of this Example wereprepared by combining the components in the amounts listed in Table 8Awith the balance being DI water and adjusting the pH of the compositionsto the final pH listed in Table 8A with 45 wt % potassium hydroxide.

TABLE 8A Quaternary Slur- Abra- Phosphonium Malonic ry sive¹ CompoundFe(NO₃)₃ Acid H2O2 # (wt %) P[1, 1, 1, 1] (ppm) (ppm) (wt %) pH CS4 2 —362 1320 2 2.3 S21 2 100 ppm 362 1320 2 2.3 (0.01 wt %) S22 2 500 ppm362 1320 2 2.3 (0.05 wt %) S23 2 1000 ppm 362 1320 2 2.3 (0.1 wt %) S242 1500 ppm 362 1320 2 2.3 (0.15 wt %) ¹KLEBOSOL ™ 1598-B25 (−) zetapotential abrasive slurry manufactured by AZ Electronics Materials,available from The Dow Chemical Company.

The average particle size for the colloidal silica abrasive is shown inTable 8B below as well as the zeta potential. The zeta potential wasmeasured for each slurry 24 hours after make-up using a Matec ESA9800zeta acoustic analyzer for measuring zeta potential (available fromMatec Applied Sciences). Each slurry sample was placed in a cup and thezeta potential was measured using a probe. Five measurements were takenfor each sample and the average zeta potential was determined for eachsample. The average for each slurry is in Table 8B.

TABLE 8B Slurry # Particle Size (nm) Zeta Potential (mV) CS4 43 −8 S2142 −7 S22 42 −5 S23 43 +1 S24 44 +3

Although there was no indication of particle agglomeration at theconcentrations of P[1,1,1,1] at 1000 ppm and 1500 ppm, the colloidalsilica particles went from a (−) zeta potential to a (+) zeta potentialindicating instability of the CMP compositions containing P[1,1,1,1] at1000 ppm and 1500 ppm.

Example 9 Quaternary Phosphonium Slurry Formulations and Stability Test

The chemical mechanical polishing compositions of this Example wereprepared by combining the components in the amounts listed in Table 9Awith the balance being DI water and adjusting the pH of the compositionsto the final pH listed in Table 9A with 45 wt % potassium hydroxide.

TABLE 9A Quaternary Slur- Abra- Phosphonium Malonic ry sive¹ CompoundFe(NO₃)₃ Acid H₂O₂ # (wt %) P[4, 4, 4, 16] (ppm) (ppm) (wt %) pH CS4 2 —362 1320 2 2.3 S25 2 30 ppm 362 1320 2 2.3 (0.003 wt %) S26 2 50 ppm 3621320 2 2.3 (0.005 wt %) S27 2 150 ppm 362 1320 2 2.3 (0.015 wt %) S28 21000 ppm 362 1320 2 2.3 (0.1 wt %) S29 2 1500 ppm 362 1320 2 2.3 (0.15wt %) ¹KLEBOSOL ™ 1598-B25 (−) zeta potential abrasive slurrymanufactured by AZ Electronics Materials, available from The DowChemical Company.

The average particle size for the colloidal silica abrasive is shown inTable 9B below as well as the zeta potential. The zeta potentials weremeasured using the Matec ESA9800 zeta acoustic analyzer as describedabove in Example 8. The average zeta potentials for each slurry in inTable 9B.

TABLE 9B Slurry # Particle Size (nm) Zeta Potential (mV) CS4 43 −8 S2566 −6 S26 72 −7 S27 168 −4 S28 6526 +89 S29 6169 +96

In addition to the zeta potential of the colloidal silica particlesgoing from a (−) potential to a (+) potential, the large increase inparticle size for P[4,4,4,16] at concentrations of 1000 ppm and 1500 ppmindicated that there was severe aggregation of the particles.Precipitate was also observed at both P[4,4,4,16] concentrations. TheCMP formulations of P[4,4,4,16] at concentrations of 1000 ppm and 1500ppm were unstable.

Example 10 (Comparative) Quaternary Phosphonium Hydroxide Salt SlurryFormulations

The chemical mechanical polishing compositions of this ComparativeExample were prepared by combining the components in the amounts listedin Table 10 with the balance being DI water and adjusting the pH of thecompositions to the final pH listed in Table 10 with 45 wt % potassiumhydroxide.

TABLE 10 Quaternary Slur- Abra- Phosphonium Malonic ry sive¹ HydroxideFe(NO₃)₃ Acid H₂O₂ # (wt %) Salt (ppm) (ppm) (ppm) (wt %) pH CS1 2 — 3621320 2 2.3 SC1 2 P[4, 4, 4, 4] 50 362 1320 2 2.3 SC2 2 P[4, 4, 4, 4] 250362 1320 2 2.3 SC3 2 P[4, 4, 4, 4] 1000 362 1320 2 2.3 ¹KLEBOSOL ™1598-B25 (−) zeta potential abrasive slurry manufactured by AZElectronics Materials, available from The Dow Chemical Company.

Example 11 (Comparative) Corrosion Rate Inhibition Performance ofQuaternary Phosphonium Hydroxide Salt CMP Slurries

Corrosion tests were carried out for the CMP comparative slurriesdisclosed in Table 10 by immersing W blanket wafers (1 cm×4 cm) in 15 gslurry samples according to the procedure described in Example 2 above.The results are disclosed in Table 11.

TABLE 11 Slurry # W Corrosion Rate (Å/min) CS1 28 SC1 31 SC2 34 SC3 36

The results in Table 11 show that the hydroxide salt of the quaternaryphosphonium compound P[4,4,4,4] increased the corrosion rate of theslurry.

Example 12 (Comparative) Quaternary Phosphonium Hydroxide Salt SlurryFormulations and Stability Test

The chemical mechanical polishing compositions of this Example wereprepared by combining the components in the amounts listed in Table 12Awith the balance being DI water and adjusting the pH of the compositionsto the final pH listed in Table 12A with 45 wt % potassium hydroxide.

TABLE 12A Quaternary Phosphonium Slur- Abra- Hydroxide Malonic ry sive¹Salt Fe(NO₃)₃ Acid H₂O₂ # (wt %) P[4, 4, 4, 4] (PPm) (PPm) (wt %) pH CS42 — 362 1320 2 2.3 SC4 2 100 ppm 362 1320 2 2.3 (0.01 wt %) SC5 2 500ppm 362 1320 2 2.3 (0.05 wt %) SC6 2 1000 ppm 362 1320 2 2.3 (0.1 wt %)SC7 2 1500 ppm 362 1320 2 2.3 (0.15 wt %) ¹KLEBOSOL ™ 1598-B25 (−) zetapotential abrasive slurry manufactured by AZ Electronics Materials,available from The Dow Chemical Company.

The average particle size for the colloidal silica abrasive is shown inTable 12B below as well as the zeta potential. The zeta potential forthe comparative slurries was measured using the Matec ESA9800 zetaacoustic analyzer as described above in Example 8. The average valuesfor the zeta potentials are in Table 12B.

TABLE 12B Slurry # Particle Size (nm) Zeta Potential (mV) CS4 43 −8 SC442 — SC5 42 +3 SC6 43 +8 SC7 44 +7

Although there was no indication of particle agglomeration ofP[4,4,4,4], the colloidal silica particles went from a (−) zetapotential to a (+) zeta potential substantially immediately after thecolloidal silica particles were mixed with the P[4,4,4,4] at all fourconcentrations, thus indicating instability of the slurries.

What is claimed is:
 1. A composition for chemical mechanical polishingtungsten comprising: water; an oxidizing agent; a colloidal silicaabrasive having a permanent negative zeta potential; a dicarboxylicacid, a source of iron (III) ions; and, optionally, a pH adjustingagent; a quaternary phosphonium compound in amounts of less than 1000ppm but greater than 0 ppm, wherein the quaternary phosphonium compoundhas a formula:

wherein R₁, R₂, R₃ and R₄ independently comprise hydrogen; linear orbranched alkyl; linear or branched hydroxyalkyl; linear or branchedalkoxy; linear or branched, aminoalkyl; linear or branched haloalkyl;linear or branched carboxyalkyl; acetonyl; substituted or unsubstitutedaryl; substituted or unsubstituted arylalkyl; substituted orunsubstituted phenylalkoxy; allyl; phosphoniumalkyl moiety; or aheterocyclic alkyl moiety; with the proviso that R₁, R₂, R₃, R₄ are notall hydrogen at the same instance and are not all butyl at the sameinstance; and X⁻ is a halide ion or hydroxide ion.
 2. The composition ofclaim 1, wherein the chemical mechanical polishing composition fortungsten comprises, as initial components: the water; 0.01 to 10 wt% ofthe oxidizing agent, wherein the oxidizing agent is hydrogen peroxide;0.01 to 10 wt% of the colloidal silica abrasive having the permanentnegative zeta potential; 100 to 1,400 ppm of the dicarboxylic acid, saltthereof or mixtures thereof, wherein the dicarboxylic acid, salt thereofor mixtures thereof is malonic acid, salt thereof or mixtures thereof;100 to 1,000 ppm of the source of iron (III) ions, wherein the source ofiron (III) ions is ferric nitrate nonahydrate; optionally the pHadjusting agent, and wherein the chemical mechanical polishingcomposition has a pH from 1 to 7; and wherein the quaternary phosphoniumcompound is in amounts of 5 to 500 ppm, wherein R₁, R_(2,) R₃ and R₄independently comprise hydrogen; linear or branched (C₁-C₁₆)alkyl;linear or branched hydroxy(C₁-C₄)alkyl; linear or branched(C₁-C₄)alkoxy; linear or branched, amino(C₁-C₄)alkyl; linear or branchedhalo(C₁-C₄)alkyl; linear or branched carboxy(C₁-C₄)alkyl; substituted orunsubstituted phenyl; substituted or unsubstituted phenyl(C₁-C₄)alkyl;substituted or unsubstituted phenyl(C₁-C₄)alkoxy;(C₂-C₄)alkylphosphonium moiety; or a heterocyclic(C₁-C₃)alkyl moiety;with the proviso that R₁, R_(2,) R₃ and R₄ are not all hydrogen at thesame instance and all are not butyl at the same instance; and X⁻ isbromide, chloride or fluoride.
 3. The composition of claim 1, whereinthe chemical mechanical polishing composition for tungsten comprises, asinitial components: the water; 1 to 3 wt% of the oxidizing agent,wherein the oxidizing agent is hydrogen peroxide; 2 to 4 wt% of thecolloidal silica abrasive having the permanent negative zeta potential;120 to 1,350 ppm of the dicarboxylic acid, salt thereof or mixturesthereof, wherein the dicarboxylic acid, salt thereof or mixtures thereofis malonic acid, salt thereof or mixtures thereof; 250 to 400 ppm of thesource of iron (III) ions, wherein the source of iron (III) ions isferric nitrate nonahydrate; optionally the pH adjusting agent, andwherein the chemical mechanical polishing composition has a pH from 2 to3; and wherein the quaternary phosphonium compound is in amounts of 10to 100 ppm, wherein the quaternary phosphonium compound is in amounts of10 ppm to 100 ppm, wherein R₁, R_(2,) R₃ and R4 independently comprisehydrogen; linear or branched (C₄-C₁₆)alkyl; linear or branchedhydroxy(C₁-C₄)alkyl; linear or branched, amino(C₁-C₄)alkyl; linear orbranched halo(C₁-C₄)alkyl; substituted or unsubstituted phenyl; orsubstituted or unsubstituted phenyl(C₁-C₄)alkyl; with the proviso thatR₁, R_(2,) R_(3,) R₄ are not all hydrogen at the same instance and notall are butyl at the same instance; and X⁻ is bromide or chloride.